This invention relates to a forage harvester and more particularly to an improved sharpening mechanism for sharpening the knives of the forage harvester cutterhead.
As is well known, sharp knives on a forage harvester cutterhead are essential for the efficient operation of the machine, and during operation of the machine, the knives should be sharpened at relatively frequent intervals, in some cases at least once a day. To that end, it is known to provide a knife sharpening device as an integral part of a forage harvester, so that the knives can be sharpened in the field without removing the knives or adding separate sharpening attachments. Such integral sharpening devices have generally taken the form of a grinding stone mounted in a carrier that is adjustable toward and away from the cutterhead periphery, the carrier also being reciprocatable across the width of the cutterhead. To sharpen the knives, the grinding stone is brought into engagement with the cutterhead periphery as the cutterhead is rotated and the grinding stone is then reciprocated back and forth across the width of the cutterhead to remove material from the cutterhead periphery and resharpen the knife cutting edges. As described in U.S. Pat. No. 3,677,316, it has been found highly desirable to rotate the cutterhead in a reverse direction during the sharpening process, a sharpening mechanism of the above general type being described in said patent wherein the sharpening stone is mounted in a carrier that is slidable along a supporting structure that is shiftable toward and away from the cutterhead periphery by means of a crank extending downwardly through the top of the cutterhead housing, the carrier being moved back and forth across the width of the cutterhead by means of handle that is manipulated by an operator standing alongside the cutterhead housing. Additional sharpening mechanisms of the above general type are shown in U.S. Pat. Nos. 3,331,167 and 3,370,628.
It is conventional in such machines to provide an access door in the cutterhead housing to provide access to the cutterhead. During the sharpening process, the operator is tempted to leave the access door open to observe the sharpening process, exposing himself to danger not only from the rotating cutterhead but also from the material expelled from the cutterhead during the sharpening process.